I suppose they either mean to live, but I can't seem to figure their difference in a sentence.
살다 is the base form of the word, that is, the form you find in the dictionary. The stem of this verb is
살-, and you add different suffices to the stem to add different meanings.
살고 있다 is composed of the stem
살- + suffix
-고 있다 adds a sense of "present progressive". If you speak Japanese, compare the suffix
Quote from howtostudykorean.com,
Attaching ~고 있다 to the stem of verbs gives it the meaning of “I am ____ ing,” – as in, I am currently doing something. It is called the “present progressive” because the action is being done in the present, and is currently “progressing” as time goes on.
Note that the suffix can be used for any grammatical person, not only "I" as the text implies.